If you run the pump and lift up on the air flap, you get no fuel flowing out the injector lines? Is that what you're saying?
If fuel is flowing in, then the metering piston may just be gummed up in position, it's easy to take apart.
The instructions and photos are in the factory 99 and 8-valve C900 manuals if you have one, but this gist of it is:
1) Take the whole distribution block / air filter housing out, be careful with the injector lines, remove the air boot that goes to the throttle body
2) Clean around the top of the fuel block really well (where the injector lines come out)
3) Remove all the lines
3) Remove the 4 screws that hold the upper part of the distribution block on, I think they are flat-heads.
4) Lay it on it's side, and carefully pull the block straight off (the metering needle will fall out the bottom if you leave it vertical)
5) You should see the metering plunger in the center of the underside of the block, and the needle roller on the air flap shaft that pushes on the metering plunger.
6) If you can, slide the metering plunger out the bottom. Be VERY careful not to drop or scratch it, it's hard chrome plated and is a very very tight fit in the distribution block
6b) If you can't slide it out, soak the whole block in acetone, or carb cleaner, or gasoline with injection cleaner in it for a while and try to get the metering plunger loosened up.
7) Once you get the metering plunger out, carefully clean out any varnish you find, and flush all of the passages in the metering block liberally with brake cleaner. You should be able to blow solvent down into where the little piston plunger goes and it should come out of the injector ports on the other side. You can use compressed air too. Don't clean the piston plunger with anything that might scratch it, like steel wool or scotchbrite, just solvent and a rag. If it's really varnishy, maybe some brass wool or something much much softer than the chrome plating.
8) Find the fuel return port banjo fitting. Next to it is a hex headed plug. That's the pressure regulating valve, works just like the oil pressure regulating valve in the engine. It's a spring loaded pin. Unscrew the hex plug, and carefully pull out the pin and the spring, make sure that passage is clear too.
9) Once everything is clean, make sure that you can easily slide the regulating piston in and out of it's bore in the distribution block. It should not hang up or catch or bind, and should be a very tight smooth fit. The clearance between the block and the plunger is less than 0.001", I believe they are lapped together to be a very precise fit
10) Make sure the air metering flap moves smoothly up and down, that the air disc is centered in air flow housing, and that the roller bearing that the regulating piston sits on turns smoothly. You can put a little bit of grease where it touches if you want.
11) Carefully re-assemble everything, the fuel pressure regulating valve, regulating piston, and distribution block, making sure you didn't introduce any dirt or grit into any of the passages.
Then run the pump and lift up on the air plate, and you should get fuel flowing out the distribution ports. Then you can move on to hooking the injectors back up and see how their spray pattern is.
The part you are removing and that gets seized in place from varnish from sitting is labelled here as the 'control plunger.'
